Method for producing chlorous acid aqueous solution by adsorption of chlorine dioxide

ABSTRACT

The present invention addresses the problem of providing a novel technique for producing aqueous chlorous acid. The present invention provides a method for producing chlorous acid, which comprises a step of adding chlorine dioxide (ClO2) to one or more components independently selected from an inorganic acid, an inorganic acid salt, an organic acid and an organic acid salt or a combination of two or more of the aforementioned components. In the method, chlorine dioxide (ClO2) is provided in the form of a gas. The method also comprises, subsequent to the above-mentioned addition step, a step of further adding one or more components independently selected from an inorganic acid, an inorganic acid salt, an organic acid and an organic acid salt or a combination of two or more of the aforementioned components.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a chlorousacid aqueous solution by chlorine dioxide adsorption.

BACKGROUND ART

Chlorous acid aqueous solution has drawn attention as a food additive.However, a chlorous acid aqueous solution is problematic in that themanufacture thereof is difficult, and even if the manufacture werepossible, the storage in normal condition is not possible.

Meanwhile, the inventors have discovered a method of manufacture of achlorous acid aqueous solution and have confirmed a sterilizing effecton E. coli, which has led to the filing of a patent application (PatentLiterature 1).

CITATION LIST Patent Literature

-   [PTL 1] International Publication No. WO 2008/026607

SUMMARY OF INVENTION Solution to Problem

The present invention has discovered, and provides, a technique relatedto a novel method of manufacturing a chlorous acid aqueous solution.

In one aspect, the present invention provides a method of trapping(capturing or adsorbing) chlorine dioxide gas (ClO₂) with one of aninorganic acid, inorganic acid salt, organic acid, and organic acidsalt, two or more types thereof or a combination thereof to create atransitional state and delay a decomposition reaction, such thatchlorous acid (HClO₂) can be stably maintained in water over a longperiod of time. A preferred embodiment of these methods can utilize afurther addition of one of an inorganic acid, inorganic acid salt,organic acid, and organic acid salt, two or more types thereof or acombination thereof to the above-described aqueous solution.

Examples of the above-described inorganic acid include carbonic acid,phosphoric acid, boric acid, and sulfuric acid. Further, examples ofinorganic acid salt include carbonate, hydroxide, phosphate, and borate.More specifically, sodium carbonate, potassium carbonate, sodiumbicarbonate, potassium bicarbonate or the like may be used as thecarbonate; sodium hydroxide, potassium hydroxide, calcium hydroxide,barium hydroxide or the like may be used as the hydroxide; disodiumhydrogen phosphate, sodium dihydrogen phosphate, trisodium phosphate,tripotassium phosphate, dipotassium hydrogen phosphate, potassiumdihydrogen phosphate or the like may be used as the phosphate; andsodium borate, potassium borate or the like may be used as the borate.Furthermore, examples of the above-described organic acid includesuccinic acid, citric acid, malic acid, acetic acid, lactic acid and thelike. Further, the following are suitable as the organic acid salt:sodium succinate, potassium succinate, sodium citrate, potassiumcitrate, sodium malate, potassium malate, sodium acetate, potassiumacetate, sodium lactate, potassium lactate, calcium lactate and thelike.

The present invention also provides the following.

-   (1) A method of manufacturing a chlorous acid aqueous solution,    comprising the step of: adsorbing (trapping) chlorine dioxide (ClO₂)    to aqueous solution A comprising one of an inorganic acid, inorganic    acid salt, organic acid, and organic acid salt, two or more types    thereof or a combination thereof.-   (2) The method of item 1, further comprising the step of adding the    chlorine dioxide in the presence of hydrogen peroxide.-   (3) The method of item 1 or 2, wherein a pH of the aqueous solution    A is 11.0 or less and 6.0 or greater.-   (4) The method of any one of items 1 to 3, wherein a pH of the    aqueous solution A is 10.8 or less and 10.2 or greater.-   (5) The method of any one of items 1 to 4, wherein TAL of the    aqueous solution A is 20 to 2000, wherein the TAL is found by an    amount of 0.1N-HCl titration from an initial pH at or below pH of    11.0 to a pH of 4, where the TAL is TAL of the aqueous solution    prior to blowing in chlorine dioxide gas, and the aqueous solution    prepared after blowing in is a chlorous acid aqueous solution. The    aqueous solution at this time has a reduced TAL relative to aqueous    solution A. A specific buffering agent (aqueous solution B) as    designated in the present invention is added to the aqueous solution    to stabilize chlorous acid and chlorite ions. The reason for keeping    the initial pH of aqueous solution A low and limiting the range of    TAL is to eliminate strong alkaline buffering power unique to sodium    hydroxide and to limit an aqueous solution to having buffering power    to weakly acidic region to weakly alkaline region.-   (6) The method of any one of items 1 to 5, wherein the chlorine    dioxide (ClO₂) is provided as gas.-   (7) The method of any one of items 1 to 6, comprising, after the    step of adding, a step of further adding aqueous solution B    comprising one of an inorganic acid, inorganic acid salt, organic    acid, and organic acid salt, two or more types thereof or a    combination thereof.-   (8) The method of any one of items 1 to 7, wherein the inorganic    acid is carbonic acid, phosphoric acid, boric acid, or sulfuric    acid.-   (9) The method of anyone of items 1 to 8, wherein the inorganic acid    salt is carbonate, hydroxide, phosphate, or borate.-   (10) The method of item 9, wherein the carbonate is sodium    carbonate, potassium carbonate, sodium bicarbonate, or potassium    bicarbonate.-   (11) The method of item 9, wherein the hydroxide is sodium    hydroxide, potassium hydroxide, calcium hydroxide, or barium    hydroxide.-   (12) The method of item 9, wherein the phosphate is disodium    hydrogen phosphate, sodium dihydrogen phosphate, trisodium    phosphate, tripotassium phosphate, dipotassium hydrogen phosphate,    or potassium dihydrogen phosphate.-   (13) The method of item 9, wherein the borate is sodium borate or    potassium borate.-   (14) The method of any one of items 1 to 13, wherein the organic    acid salt is succinic acid, citric acid, malic acid, acetic acid, or    lactic acid.-   (15) The method of any one of items 1 to 14, wherein the organic    acid salt is sodium succinate, potassium succinate, sodium citrate,    potassium citrate, sodium malate, potassium malate, sodium acetate,    potassium acetate, sodium lactate, potassium lactate, or calcium    lactate.-   (16) The method of any one of items 4 to 15, wherein a pH of a    liquid after adding the aqueous solution B is 3.2 or greater and    less than 7.0.-   (17) The method of any one of items 4 to 16, wherein a pH of a    liquid after adding the aqueous solution B is 4.0 or greater and    less than 7.0.-   (18) The method of any one of items 4 to 17, wherein a pH of a    liquid after adding the aqueous solution B is 5.0 or greater and    less than 7.0.-   (19) The method of anyone of items 1 to 18, wherein the chlorine    dioxide is present at a concentration of 0.8 to 1.0%.-   (20) A chlorous acid aqueous solution manufactured by a method    comprising the step of trapping chlorine dioxide (ClO₂) with aqueous    solution A comprising one of an inorganic acid, inorganic acid salt,    organic acid, and organic acid salt, two or more types thereof or a    combination thereof.-   (21) The chlorous acid aqueous solution of item 20, wherein the    method further comprises a step of adding the chlorine dioxide in    the presence of hydrogen peroxide.-   (22) The chlorous acid aqueous solution of item 20 or 21, wherein a    pH of the aqueous solution A is 11.0 or less and 6.0 or greater.-   (23) The chlorous acid aqueous solution of any one of items 20 to    22, wherein a pH of the aqueous solution A is 10.8 or less and 10.2    or greater.-   (24)

The chlorous acid aqueous solution of any one of items 20 to 22, whereinthe chlorine dioxide (ClO₂) is provided as gas.

Additional embodiments and advantages of the present invention arerecognized by those skilled in the art who read and understand thefollowing detailed description as needed.

Advantageous Effects of Invention

According to the present invention, a technique is provided forstabilizing chlorous acid, which is a useful substance, in an aqueoussolution for a long period of time, such that the possibility of utilityhas improved as a chlorous acid aqueous solution that is convenient forhandling in a wide range of applications in not only the food industry,but also in many fields such as welfare and nursing facilities andmedical facilities.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a schematic diagram of a manufacturing plant used in theExamples. Each symbol represents the following: 1: chlorous acid aqueoussolution manufacturing tank; 2: gas washing device; 3: chlorine dioxidegas storage tank; 4: air pump; 5: air flow spigot.

FIG. 2 shows the UV spectrum in Example 1. A double peak is observed.

FIG. 3 shows the UV spectrum in Example 2. A double peak is observed.

FIG. 4 shows the UV spectrum in Example 3. A double peak is observed.

FIG. 5 shows the UV spectrum in Example 4. A double peak is observed.

FIG. 6 shows the UV spectrum in Example 5. A double peak is observed.

FIG. 7 shows the UV spectrum in Example 6. A double peak is observed.

FIG. 8 shows the stability of the chlorous acid aqueous solutionsmanufactured in Examples 2 and 4 compared to the control, which wasconducted in Example 7. The horizontal axis indicates the number ofdays, and the vertical axis indicates the chlorous acid concentration.

DESCRIPTION OF EMBODIMENTS

The present invention is described hereinafter. Throughout the entirespecification, a singular expression should be understood asencompassing the concept thereof in the plural form, unless specificallynoted otherwise. Thus, singular articles (e.g., “a”, “an”, “the” and thelike in case of English) should also be understood as encompassing theconcept thereof in the plural form unless specifically noted otherwise.Further, the terms used herein should be understood as being used in themeaning that is commonly used in the art, unless specifically notedotherwise. Thus, unless defined otherwise, all terminologies andscientific technical terms that are used herein have the same meaning asthe terms commonly understood by those skilled in the art to which thepresent invention pertains. In case of a contradiction, the presentspecification (including the definitions) takes precedence.

As used herein “chlorous acid aqueous solution” refers to an aqueoussolution comprising chlorous acid (HClO₂) that is used as a sterilizingagent. The chlorous acid aqueous solution of the present inventioncreates a transitional state and delays a decomposition reaction, suchthat chlorous acid (HClO₂) can be stably maintained over a long periodof time. When a sample of chlorous acid aqueous solution is measuredwith a spectrophotometer, the presence of a chlorous acid aqueoussolution can be confirmed when an absorbent section comprising an acidicchlorite ion (H+ClO₂) representing a peak near 260 nm and an absorbentsection comprising chlorine dioxide (ClO₂) representing a peak near 350nm can be simultaneously confirmed between wavelengths 240 to 420 nm inthe UV spectrum, i.e., when a double peak is exhibited. In such a case,it is understood that a cyclic reaction involving the main constituentchlorous acid (HClO₂), chlorine dioxide (ClO₂), and acidic chlorite ion(H⁺+ClO₂ ⁻) is simultaneously in progress.

As used herein, the term “chlorous acid aqueous solution” may encompassa “chlorous acid aqueous solution formulation”. A chlorous acid aqueoussolution formulation can be manufactured by using a chlorous acidaqueous solution manufactured by the manufacturing method of the presentinvention and blending in aqueous solution B. A representativeconstitution of a chlorous acid aqueous solution formulation that can bemixed and used is 60.00% (w/v) chlorous acid aqueous solution (5%product) (chlorous acid concentration is 50000 ppm), 1.70% (w/v)potassium dihydrogen phosphate, 0.50% (w/v) potassium hydroxide, and37.8% purified water (sold under the name “AUTOLOC Super” by theApplicant), but the constitution is not limited thereto. When thisconstitution of mixture is used, the chlorous acid aqueous solution maybe 0.25% (w/v) to 75% (w/v), potassium dihydrogen phosphate may be 0.70%(w/v) to 13.90% (w/v), and potassium hydroxide may be 0.10% (w/v) to5.60% (w/v). It is also possible to use sodium dihydrogen phosphateinstead of potassium dihydrogen phosphate, and sodium hydroxide insteadof potassium hydroxide.

As used herein, “stability” of a chlorous acid aqueous solution refersto a state of maintaining chlorous acid (HClO₂).

As used herein, “antimicrobial (action)” refers to suppression of growthof pathogenic, harmful, or infectious microorganisms such as mold,microbes, or viruses. A substance having antimicrobial action isreferred to as an antimicrobial agent.

As used herein, “sterilizing (action)” refers to killing of pathogenic,harmful, or infectious microorganisms such as mold, microbes, orviruses. A substance having sterilizing action is referred to as asterilizing agent.

As used herein, “microbe-removing (action)” refers to removal ofpathogenic, harmful, or infectious microorganisms such as mold,microbes, or viruses. A substance having microbe-removing action isreferred to as a micro-removing agent.

As used herein, “disinfecting (action)” refers to disinfection ofpathogenic, harmful, or infectious microorganisms such as mold,microbes, or viruses. A substance having disinfecting action is referredto as a disinfecting agent.

Antimicrobial action, sterilizing action, microbe-removing action, anddisinfecting action are collectively referred to as germicidal (action),which is used herein as a broad concept encompassing antimicrobial(action), sterilizing (action), microbe-removing (action), anddisinfecting (action) unless specifically noted otherwise. Thus,substances having antimicrobial action, sterilizing action,microbe-removing action, or disinfecting action collectively referredherein as a “sterilizing agent”, which is understood as an agent alsohaving action corresponding to antimicrobial action, sterilizing action,microbe-removing action, and disinfecting action in general use herein.

As used herein, an article used with a manufactured chlorous acidaqueous solution is any article that can be impregnated with thechlorous acid aqueous solution to be used in sterilization or the like,including medical devices. Examples thereof include, but are not limitedto, a sheet, film, patch, brush, nonwoven fabric, paper, fabric,absorbent cotton, sponge and the like. Further, any material may beused, as long as a chlorous acid aqueous solution can be impregnatedtherein.

As used herein, “TAL” is used to measure alkalinity of a sample bytitrating 0.1 mol/L hydrochloric acid-standard acid solution until asample has a pH of 4.0, wherein alkalinity (TAL) is 1 when 1 mL of 0.1mol/L hydrochloric acid is required to make 100 g of sample to have a pHof 4.0. A pH of 4.0 is the second neutralization point for sodiumcarbonate.

(Chlorous Acid Aqueous Solution and Manufacturing Example Thereof)

The chlorous acid aqueous solution used in the present invention has afeature and function that was discovered by the inventors.

The present invention relates to a method that is different from knownmanufacturing methods, such as those described in Patent Literature 1.

Specifically, conventional techniques added and reacted sulfuric acid oran aqueous solution thereof, with an aqueous sodium chlorate solution,in an amount and concentration at which the pH value of the aqueoussodium chlorate solution can be maintained from 2.3 to 3.4 to generatechloric acid, and then added hydrogen peroxide in an amount equivalentto or greater than the amount required for a reduction reaction of thechloric acid. However, the feature of the present invention isaccomplished by providing a method of manufacturing chlorous acidcomprising the step of adding chlorine dioxide gas (ClO₂), instead ofadding hydrogen peroxide to chloric acid, to one of an inorganic acid,inorganic acid salt, organic acid, and organic acid salt, two or moretypes thereof or a combination thereof (aqueous solution A). Use ofchlorine dioxide gas (gas) is beneficial in that it generates chloriteions with a high level of alkalinity and lowers the pH to neutral orlower, and then some of the chlorite ions transition to a state ofchlorous acid to create a transitional state, resulting in delaying adecomposition reaction, such that chlorous acid (HClO₂) can be stablymaintained over a long period of time. Such an effect can beaccomplished by trapping chlorine dioxide (ClO₂) with aqueous solution Acomprising one of an inorganic acid, inorganic acid salt, organic acid,and organic acid salt, two or more types thereof or a combinationthereof. The expression “trap” may refer to adsorption, capture or thelike, preferably any manipulation leading to co-existence of gaseouschlorine dioxide with one of an inorganic acid, inorganic acid salt,organic acid, and organic acid salt, two or more types thereof or acombination thereof. Examples of such a manipulation generally include,but are not limited to, a method of directly blowing in gas into aqueoussolution A, a method of adsorption by spraying aqueous solution A like amist from the top and releasing chlorine dioxide gas from the bottom,air blast and the like. Although not wishing to be bound by any theory,the chlorous acid aqueous solution of the present invention manufacturedby using a manufacturing plant as shown in FIG. 1 (see Examples 1 to 6)is demonstrated as exhibiting a stable sterilizing effect at least underrefrigerated condition (4° C.) for 10 days as shown in Example 7. Thus,the present invention is understood as providing a manufacturing methodof stable chlorous acid in an aqueous solution, the so-called chlorousacid aqueous solution.

A chlorous acid aqueous solution formulation can be manufactured bymixing in aqueous solution B with a chlorous acid aqueous solutionmanufactured by the manufacturing method of the present invention. Arepresentative constitution of such a formulation that can be mixed andused is, for example, 60.00% (w/v) chlorous acid aqueous solution (5%product) (chlorous acid concentration is 50000 ppm), 1.70% (w/v)potassium dihydrogen phosphate, 0.50% (w/v) potassium hydroxide, and37.8% purified water (sold under the name “AUTOLOC Super” by theApplicant), but the constitution is not limited thereto. When thisconstitution of mixture is used, the chlorous acid aqueous solution maybe 0.25% (w/v) to 75% (w/v), potassium dihydrogen phosphate may be 0.70%(w/v) to 13.90% (w/v), and potassium hydroxide may be 0.10% (w/v) to5.60% (w/v). It is also possible to use sodium dihydrogen phosphateinstead of potassium dihydrogen phosphate, and sodium hydroxide insteadof potassium hydroxide. Although this agent reduces the deterioration ofchlorous acid due to contact with an organic matter under acidicconditions, the sterilizing effect is maintained. In addition, verylittle chlorine gas is generated. The agent also has a feature ofgenerating an insignificant amount of chlorine gas, thus reducingamplification of chlorine odor generated from reacting chlorine with anorganic matter.

Conventional manufacturing methods generate a chlorous acid aqueoussolution by adding and reacting sulfuric acid or an aqueous solutionthereof, with an aqueous sodium chlorate solution, in an amount andconcentration at which the pH value of the aqueous sodium chloratesolution can be maintained at 3.4 or lower to generate chloric acid, andthen adding hydrogen peroxide in an amount equivalent to or greater thanthe amount required for a reduction reaction of the chloric acid. Thepresent invention is significantly different in terms of the use ofchlorine dioxide gas. A difference is also found in the use of chlorinedioxide gas creating a transitional state and delaying a decompositionreaction, such that chlorous acid (HClO₂) can be stably maintained overa long period of time. In addition, the present invention ischaracterized in that a raw material for generating chlorine dioxide gasdoes not need to be specified by utilizing chlorine dioxide as the rawmaterial. For instance, chlorine dioxide gas is generated in addition toacidified sodium chlorite (ASC) when sodium chlorite is added to acid.However, such chlorine dioxide gas can be utilized to manufacture achlorous acid aqueous solution. Sodium chlorite is a highly alkalinesubstance that is integrated with an alkaline substance to be stable.Sodium chlorite needs to be in a state of acidified sodium chlorite(ASC) to exert an effect for use as a sterilizing agent. However, use ofthis method can also lead to manufacture of a chlorous acid aqueoussolution, which is a liquid product, by using as a raw material, agasified chlorine dioxide separately generated from acidified sodiumchlorite, which is a liquid product. Furthermore, due to theelectrolysis process in the manufacture of a chlorous acid aqueoussolution from sodium chloride, there was a risk of bromide ions in thesodium chloride changing into a carcinogenic substance bromic acid andcontaminating the chlorous acid aqueous solution. However, since themanufacturing method of the present invention uses chlorine dioxide gaswhich is gas, such a risk of carcinogenic substance contamination hasbeen eliminated. Use of chlorine dioxide gas as a raw material ischaracterized in further facilitating the manufacture of chlorous acidaqueous solution because there would be no need to consider thepreceding process. In addition, since generation of chlorine dioxide gasis not preferable in a manufacturing method from sodium chlorite, it isconsidered desirable to increase alkalinity. A pH closer to isconsidered more preferable. Thus, a method of manufacturing sodiumchlorite is recognized as performing the complete opposite of thepresent method, which manufactures a chlorous acid aqueous solution byusing aqueous solution A, which is neutral to weakly alkaline, e.g., pHof 6.0 to the order of 11.0 shown in the present invention.

In one embodiment, the chlorine dioxide gas (ClO₂) is provided as gas.In a specific embodiment, chlorine dioxide gas (ClO₂) is gas that isused with a concentration of 0.8 to 1.0% (e.g., the acceptable range is0.9%±0.1%). One preferred concentration is 0.88%, but is not limitedthereto. Gas with a high concentration is dangerous due to itsexplosiveness. Thus, such gas is diluted with nitrogen gas or the likefor use.

In one embodiment, the chlorine dioxide gas is added in the presence ofhydrogen peroxide (H₂O₂). In another embodiment, the aqueous solution Amay contain hydrogen peroxide, and the chlorine dioxide gas is trappedwith aqueous solution A containing hydrogen peroxide. Coexistence ofchlorine dioxide gas with hydrogen peroxide (H₂O₂) suppresses thegeneration of chlorate ions and generates chlorous acid (HClO₂) throughthe so-called “cyclic reaction” where chlorite ions, chlorous acid, andaqueous chlorine dioxide are simultaneously present.

A preferred embodiment comprises, after the step of adding, the step offurther adding one of an inorganic acid, inorganic acid salt, organicacid, and organic acid salt, two or more types thereof or a combinationthereof. This is because the pH or the like can be adjusted to adjustthe transitional state by further adding a step in this manner.

Further, in another embodiment, carbonic acid, phosphoric acid, boricacid, or sulfuric acid can be used as inorganic acid in theabove-described method, but phosphoric acid is preferred. Although notwishing to be bound by any theory, the present invention is demonstratedas being able to be maintained within a suitable range of pH with a highbuffering effect in a state of chlorous acid while retaining asterilizing effect by using especially phosphoric acid.

Furthermore, in another embodiment, carbonate, hydroxide, phosphate, orborate can be used as inorganic acid salt, but phosphate is preferred.Although not wishing to be bound by any theory, the present invention isdemonstrated as being able to be maintained within a suitable range ofpH with a high buffering effect in a state of chlorous acid whileretaining a sterilizing effect by using especially phosphate.

Further, in another embodiment, sodium carbonate, potassium carbonate,sodium bicarbonate, or potassium bicarbonate may be used as carbonate,but sodium carbonate is preferred. This is because pH has bufferingpower at a weakly alkaline region and weakly acidic region, such thatchlorous acid can be advantageously stabilized in this region.

Furthermore, in another embodiment, sodium hydroxide, potassiumhydroxide, calcium hydroxide, or barium hydroxide may be used ashydroxide, but potassium hydroxide or sodium hydroxide is preferred.Although not wishing to be bound by any theory, such hydroxides can beused to increase chlorous acid content. Meanwhile, use of a divalentsalt maybe advantageous because desalination is possible in combined usewith phosphoric acid such that the amount of salt to chlorous acid andchlorite ions can be reduced.

Furthermore, in another embodiment, disodium hydrogen phosphate, sodiumdihydrogen phosphate, trisodium phosphate, tripotassium phosphate,dipotassium hydrogen phosphate, or potassium dihydrogen phosphate may beused as the phosphate. Preferably, dipotassium hydrogen phosphate can beused. Although not wishing to be bound by any theory, this is becausethese phosphates can have buffering power in a useful pH region exertingthe most sterilization power, which is a pH from 5 to less than 7. Thiscan be advantageous because chlorous acid can be stable in this pHregion.

Further, in another embodiment, sodium borate or potassium borate can beused as borate.

Furthermore, in another embodiment, succinic acid, citric acid, malicacid, acetic acid, lactic acid can be used as organic acid. Succinicacid can be preferably used. Although not wishing to be bound by anytheory, succinic acid can have buffering power from a pH of less than 6to 4. Drastic gasification of chlorine dioxide can be suppressed withinthis range of pH. However, pH tends to drastically decrease when pH isless than 5, in which case use of organic acid with a buffering powerwith a pH from 3 to less than 4 such as citric acid is desirable.

Furthermore, in another embodiment, sodium succinate, potassiumsuccinate, sodium citrate, potassium citrate, sodium malate, potassiummalate, sodium acetate, potassium acetate, sodium lactate, potassiumlactate, or calcium lactate can be used as organic acid salt.

In one embodiment, the advantageous initial pH of a buffering agent withchlorine dioxide blown therein is generally, but not limited to, 11.0 orless and 6.0 or greater, and more preferably 10.8 or less and 10.2 orgreater. When the initial pH is 10.8 or less and 10.2 or greater, theavailable chlorine concentration ultimately attained increases whilesuppressing generation of chlorite and the yield is improved. As usedherein, pH values are rounded to indicate one significant digit. Forinstance, when the actual measured value is a pH of 10.83, this value isshown as a pH of 10.8.

Normally, such a pH may be 11.0 or greater, where available chlorineconcentration ultimately attained increases and the yield is improved.However, use of sodium hydroxide (caustic soda) or the like is notpreferable because the use would generate sodium chlorite, which iscontradictory to the objective of the present invention. Although notwishing to be bound by any theory, when sodium chlorite is manufactured,chlorine dioxide gas is adsorbed to an aqueous solution in whichhydrogen peroxide is added to a high concentration of sodium hydroxide.The pH of the aqueous solution prior to adsorption to chlorine dioxidegas is strongly alkaline with a pH of 11.3 or greater and 12 or greaterin practice. The recovery rate would be nearly 100%. Thus, oneadsorption tank is sufficient (generally two or more adsorption tanksare required as the recovery rate is low for chlorous acid aqueoussolution), where the generated product is not chlorous acid aqueoussolution but sodium chlorite. Thus, such a pH suitable for the objectiveof the present invention may be any condition that chlorine dioxide gascould have. Atypical example includes, but is not limited to, a pH of6.0 to 11.0 and preferably 10.2 to 10.8. Examples of a preferably pH asan upper limit include, but not limited to, 11.2, 11.1, 11.0, 10.9,10.8, 10.7, 10.6, 10.5, 10.4, 10.3, 10.2, 10.1, 10.0, 9.9, 9.8, 9.7,9.6, 9.5, 9.4, 9.3, 9.2, 9.1, 9.0 and the like. Examples of preferredupper limits of pH include a value less than 11, value less than 10.5,value less than 10, valueless than 9.5, value less than 9, value lessthan 8.5, value less than 8, value less than 7.5, value less than 7,value less than 6.5 and the like. Examples of preferred low limit of pHinclude, but are not limited to, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7,6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1,8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5,9.6, 9.7, 9.8, 9.9, 10.0, 10.1, 10.2 and the like. Examples of preferredlower limit of pH include a value greater than 6, value greater than6.5, value greater than 7, value greater than 7.5, value greater than 8,value greater than 8.5, value greater than 9, value greater than 9.5,value greater than 10 and the like. Any combination of such upper limitsand lower limits can be suitable and used in the present invention.Examples of preferred combinations of an upper limit and lower limitinclude 6.0 to 6.5, 6.0 to value less than 6.5, 6.0 to 9.0, 6.0 to valueless than 9.0, 6.0 to 10.0, 6.0 to value less than 10.0, 6.0 to 11.0,6.0 to value less than 11.0, value greater than 6.0 to value of 6.5,value greater than 6.0 to value of 9.0, value greater than 6.0 to valueof 10.0, value greater than 6.0 to value of 11.0, value greater than 6.0to value less than 6.5, value greater than 6.0 to value less than 9.0,value greater than 6.0 to value less than 10.0, value greater than 6.0to value less than 11.0, 7.0 to 9.0, 7.0 to value less than 9.0, 7.0 to10.0, 7.0 to value less than 10.0, 7.0 to 11.0, 7.0 to value less than11.0, value greater than 7.0 to value of 9.0, value greater than 7.0 tovalue of 11.0, value greater than 7.0 to value less than 9.0, valuegreater than 7.0 to value less than 11.0 and the like.

When chlorine dioxide gas is adsorbed to a low concentration aqueousalkaline solution in the manufacture of a chlorous acid aqueoussolution, a small buffer zone appears between pH of 6 and 8 (normalsodium chlorite does not have such a buffer zone). A buffering agent forretaining a potent buffering power in this pH region is required tomaintain what is in this buffer region in a state of chlorous acid orchlorite ion for a long period of time. Thus, a buffering agent and arange of pH that fit this condition are preferably selected.

Although the sodium chlorite content can be increased more with strongerbuffering power from pH 14 to pH of 10, the manufacturing method of thepresent invention is for manufacturing an aqueous solution thatmaintains a cyclic reaction of chlorous acid, chlorine dioxide andchlorite ion. Thus, there is no need to raise the initial pH of aqueoussolution A, which is strongly alkaline required to manufacture sodiumchlorite, to a pH of 11.0 or greater. Since the present invention is nota method of manufacturing sodium chlorite, it is preferable to avoid acondition under which sodium chlorite is produced. Although not wishingto be bound by any theory, it is important for the present invention toenhance buffering power from the neutral to the weakly acidic region,and thus TAL (provided that the initial value is pH of 11.0 or less) wasemployed as an indicator thereof. When the pH of the manufacturedchlorous acid aqueous solution is low, a buffering agent may be newlyadded to raise the pH. In one embodiment, when the manufactured chlorousacid aqueous solution is used and mixed with a buffering agent, the pHrange may be 3.2 to 7.0.

Although there is currently no concentration that is necessarily optimalas the concentration of the blown in chlorine dioxide gas, oneembodiment can use gas with a concentration of 0.8 to 1.0% and aspecific example can use gas with a concentration of 0.88%. Although notwishing to be bound by any theory, gas with a high concentration isdangerous due to its explosiveness. Thus, such gas is generally dilutedwith nitrogen gas or the like for use.

A conventional method of manufacturing an aqueous solution (chlorousacid aqueous solution) comprising chlorous acid (HClO₂) that can be usedas a sterilizing agent would generate chlorous acid (HClO₂) by addinghydrogen peroxide (H₂O₂), to an aqueous solution of sodium chlorate(NaCl₃), in an amount required to produce chlorous acid by a reducingreaction of chloric acid (HClO₃) obtained by adding sulfuric acid(H₂SO₄) or an aqueous solution thereof to an aqueous solution of sodiumchlorate (NaClO₃) so that the aqueous solution of sodium chlorate is inan acidic condition. The basic chemical reaction of this method ofmanufacturing is represented by the following formula A and formula B.

[Chemical 1]

2NaClO₃+H₂→SO₄→2HClO₃+Na₂SO₄   (formula A)

(formula B)   [Chemical 1]

Formula A indicates that chloric acid is obtained while sodium ions areremoved by adding sulfuric acid (H₂SO₄) or an aqueous solution thereofin an amount and concentration at which the pH value of an aqueoussodium chlorate (NaClO₃) solution can be maintained within acidity.Next, formula B indicates that chloric acid (HClO₃) is reduced withhydrogen peroxide (H₂O₂) to produce chlorous acid (HClO₂).

[Chemical 2]

HClO₃+H₂O₂→2ClO₂+H₂O+O₂↑  (formula C)

2 ClO₂+H₂O₂→2 HClO₂+O₂↑  (formula D)

2 ClO₂+H₂O⇔HClO₂+HClO₃   (formala E)

2 HClO₂⇔H₂O+Cl₂O₃   (formula F)

At this time, chlorine dioxide gas (ClO₂) is generated (formula C).However, coexistence with hydrogen peroxide (H₂O₂) results in theproduction of chlorous acid (HClO₂) through the reactions in formulaeD-F. The present invention utilizes the reactions after the chlorinedioxide gas (ClO₂). Although not wishing to be bound by any theory, whenthis reaction was taken out and utilized, it was unexpectedly found thatit is possible to create a transitional state and delay a decompositionreaction, such that chlorous acid (HClO₂) can be stably maintained overa long period of time.

Meanwhile, the property of the produced chlorous acid (HClO₂) is suchthat it is decomposed early into chlorine dioxide gas or chlorine gasdue to the presence of chloride ion (Cl⁻), hypochlorous acid (HClO) andother reduction substances or a decomposition reaction occurring among aplurality of chlorous acid molecules. Thus, it is necessary to preparechlorous acid (HClO₂) such that the state of being chlorous acid (HClO₂)can be maintained for a long period of time in order to be useful as asterilizing agent.

In this regard, chlorous acid (HClO₂) can be stably maintained over along period of time by adding one of an inorganic acid, inorganic acidsalt, organic acid, and organic acid salt, two or more types thereof ora combination thereof to the chlorous acid (HClO₂), chlorine dioxide gas(ClO₂) or an aqueous solution containing them obtained by theabove-described method to create a transitional state and delay adecomposition reaction. Although not wishing to be bound by any theory,the present invention further demonstrates that a transitional state iscreated and a decomposition reaction is delayed such that chlorous acid(HClO₂) can be stably maintained over a long period of time by using,for example, a phosphoric acid buffering agent. Furthermore, althoughnot wishing to be bound by any theory, the present inventiondemonstrates that a longer and more stable transitional state can becreated and chlorous acid (HClO₂) can be maintained over a longer periodof time by delaying a decomposition reaction when using potassium salt(potassium hydroxide, potassium phosphate salt (e.g., tripotassiumphosphate, dipotassium hydrogen phosphate, or potassium dihydrogenphosphate)) as metal, in comparison to cases using sodium salt (e.g.,sodium hydroxide, sodium phosphate salt (disodium hydrogen phosphate,sodium dihydrogen phosphate, trisodium phosphate) as metal.

In one embodiment, it is possible to utilize chlorous acid (HClO₂),chlorine dioxide gas (ClO₂), or an aqueous solution containing themobtained by the above-described method, to which one of an inorganicacid and inorganic acid salt, specifically phosphate, carbonate andhydroxide, particularly phosphate and hydroxide, two or more typesthereof or a combination thereof is added.

In another embodiment, it is possible to utilize an aqueous solution towhich one of an inorganic acid and inorganic acid salt, specificallyphosphate, carbonate and hydroxide, particularly phosphate andhydroxide, two or more types thereof or a combination thereof is added,to which one of an inorganic acid, inorganic acid salt, organic acid,and organic acid salt, two or more types thereof or a combinationthereof is added.

Additionally, in another embodiment, it is possible to utilize anaqueous solution manufactured by the above-described method, to whichone of an inorganic acid, inorganic acid salt, organic acid, and organicacid salt, two or more types thereof or a combination thereof is added.

Examples of inorganic acid include, but are not limited to, carbonicacid, phosphoric acid, boric acid, and sulfuric acid, while phosphoricacid is preferable. Further, examples of inorganic salt include, but arenot limited to, carbonate and hydroxide as well as phosphate and borate,where phosphate is preferable. More specifically, sodium carbonate,potassium carbonate, sodium bicarbonate, potassium bicarbonate, or thelike maybe used as the carbonate; sodium hydroxide, potassium hydroxide,calcium hydroxide, barium hydroxide, or the like may be used as thehydroxide; disodium hydrogen phosphate, sodium dihydrogen phosphate,trisodium phosphate, tripotassium phosphate, dipotassium hydrogenphosphate, potassium dihydrogen phosphate, or the like may be used asthe phosphate; and sodium borate, potassium borate, or the like may beused as the borate, which is preferably, but not limited to, potassiumsalt. Furthermore, examples of the above-described organic acid includesuccinic acid, citric acid, malic acid, acetic acid, lactic acid and thelike. Further, sodium succinate, potassium succinate, sodium citrate,potassium citrate, sodium malate, potassium malate, sodium acetate,potassium acetate, sodium lactate, potassium lactate, calcium lactate orthe like is suitable as the organic acid salt.

When an acid and/or a salt thereof is added, a transitional state, suchas Na⁺+ClO₂ ⁻<−>Na—ClO₂, K⁺+ClO₂ ⁻<−>K—ClO₂, or H⁺+ClO₂ ⁻<−>H—ClO₂ canbe temporarily created to delay the progression of chlorous acid (HClO₂)to chlorine dioxide (ClO₂), which enables the manufacture of an aqueoussolution comprising chlorous acid (HClO₂) that maintains chlorous acid(HClO₂) for a long period of time and generates a small amount ofchlorine dioxide (ClO₂). Although not wishing to be bound by any theory,it was demonstrated in the present invention that such an effect ofmaintaining is enhanced by using a phosphoric acid buffering agent.Although not wishing to be bound by any theory, it was furtherdemonstrated in the present invention that such an effect of maintainingis further enhanced by using potassium salt relative to a case of usingsodium salt or the like.

The following represents the decomposition of chlorite in an acidicsolution in the above-described chemical formula 2.

[Chemical 3]

5ClO₂ ⁻+4H⁺→4ClO₂+5Cl⁻+2H₂O   (a)

(5Na ClO₂+4CH₂COOH→4ClO₂30 4CH₃COONa+NaCl+2H₂O) 3ClO₂ ⁻→2ClO₃ ⁻+Cl⁻  (b)

(3NaClO₂→2NaClO₃+NaCl)^(Autodecomposition) ClO₂ ⁻→Cl⁻+2O   (C)

As represented in the formula, the rate of decomposition of an aqueoussodium chlorite solution in terms of pH is higher when pH is lower,i.e., when acidity is stronger. That is, the absolute rates of thereactions (a), (b), and (c) in the above-described formula increase. Forexample, although the ratio accounted for by reaction (a) decreases fora lower pH, the total decomposition rate changes significantly, i.e.,increases. Thus, the amount of generated chlorine dioxide (ClO₂)increases with the decrease in pH. Thus, the lower the pH value resultsin earlier sterilization or bleaching. However, stimulatory and harmfulchlorine dioxide gas (ClO₂) renders an operation difficult andnegatively affects the health of a human being. Further, a reaction fromchlorous acid to chlorine dioxide progresses quickly, resulting in thechlorous acid becoming unstable. In addition, the time a sterilizationpower is maintained is very short.

In this regard, when the above-described inorganic acid, inorganic acidsalt, organic acid or organic acid salt is added to an aqueous solutioncomprising chlorous acid (HClO₂), pH values are adjusted within therange of 3.2 to 8.5, or within a preferred range such as pH 3.2 to 7.0or pH 5.0 to 7.0 in accordance with the objective, from the viewpoint ofbalancing suppression of chlorine dioxide generation and sterilizingpower.

When a spectrometric measurement of a sample can simultaneously identifyan absorbent section comprising an acidic chlorite ion (H⁺+ClO₂ ⁻)representing a peak near 260 nm and an absorbent section comprisingchlorine dioxide (ClO₂) representing a peak near 350 nm betweenwavelengths 240 to 420 nm, it is possible to recognize presence of thechlorous acid aqueous solution of the present invention, i.e., thepresence of chlorous acid (HClO₂). This is because a cyclic reactioninvolving the main constituent chlorous acid (HClO₂), chlorine dioxide(ClO₂), and acidic chlorite ion (H⁺+ClO₂ ⁻¹) is simultaneously inprogress as shown in the following Chemical Formula 4.

Conversion of chlorous acid (HClO₂) to chlorine dioxide (ClO₂) resultsin a single peak only near 350 nm.

It has already been found that pH can be further stabilized at this timeby directly adding a buffering agent or by first adjusting the pH withsodium carbonate or the like and then adding another buffering agent.

Thus, in one aspect, the present invention provides a sterilizing agentcomprising a chlorous acid aqueous solution, metal hydroxide, and metalphosphate.

Although not wishing to be bound by any theory, it was discovered thatthe present invention unexpectedly maintains a sterilizing effect whileachieving an effect of long-term storage/stability because a combinationof chlorine dioxide and one of an inorganic acid, inorganic acid salt,organic acid, and organic acid salt, two or more types thereof or acombination thereof creates a transitional state and delay adecomposition reaction such that chlorous acid (HClO₂) can be stablymaintained in water over a long period of time. Examples of preferableranges of pH include, but are not limited to, 3.2 or higher to less than7.0, about 5.0 to about 7.5, about 5.0 to about 7.0, about 5.5 to about7.0, about 5.0 to about 6.0, and the like. Examples of the lower limitinclude, but are not limited to, about 5.0, about 5.1, about 5.2, about5.3, about 5.4, about 5.5, and the like, and examples of the upper limitinclude, but are not limited to, about 7.5, about 7.4, about 7.3, about7.2, about 7.1, about 7.0, about 6.9, about 6.8, about 6.7, about 6.5,about 6.4, about 6.3, about 6.2, about 6.1, about 6.0, about 5.9, about5.8, about 5.7, about 5.6, about 5.5, and the like. The optimal pHincludes, but is not limited to, about 5.5. When “about” is used for apH value herein, the range is intended to span 0.05 in both directionswhen the significant digit is the first decimal point. For example,about 5.5 is understood as referring to 5.45 to 5.55. For the purpose ofdistinction from sodium chlorite, pH is preferably, but not limited to,less than 7.0 in the present invention.

In another aspect, although not wishing to be bound by any theory, useof potassium salt is preferable in the present invention because theproperty of being readily dissociable in an aqueous solution by usingpotassium as metal in a phosphoric acid buffering agent relative tosodium or the like was found to be effective in maintaining chlorousacid, and the use was found to enhance an effect of maintaining thecreated transitional state for a long period of time and delaying theprogression from chlorous acid (HClO₂) to chlorine dioxide (ClO₂).

Preferable metal hydroxide includes sodium hydroxide and/or potassiumhydroxide. Preferable metal phosphate includes sodium phosphate (e.g.,disodium hydrogen phosphate, sodium dihydrogen phosphate, trisodiumphosphate) and/or potassium phosphate (e.g., tripotassium phosphate,dipotassium hydrogen phosphate, and potassium dihydrogen phosphate;especially potassium dihydrogen phosphate), and still preferably,potassium hydroxide and potassium phosphate (e.g., tripotassiumphosphate, dipotassium hydrogen phosphate, and potassium dihydrogenphosphate; especially potassium dihydrogen phosphate), where the aboveare non-limiting examples.

In a preferred embodiment, sodium hydroxide and potassium hydroxide are0.1 N to 1.0 N and buffer pH of sodium phosphate and potassium phosphateis 5.0 to 7.5, especially pH of 5.0 to 7.0. This is because the effectof long term storage/stability is unexpectedly enhanced more than thepreviously-expected levels at these constitution and pH.

In one aspect, the present invention provides a chlorous acid aqueoussolution manufactured by a method comprising the step of trappingchlorine dioxide (ClO₂) with aqueous solution A comprising one of aninorganic acid, inorganic acid salt, organic acid, and organic acidsalt, two or more types thereof or a combination thereof. In a preferredembodiment, the chlorous acid aqueous solution is manufactured by themethod further comprising the step of adding the chlorine dioxide in thepresence of hydrogen peroxide. In another preferred embodiment, the pHof the aqueous solution A is 11.0 or less and 6.0 or greater in themethod. In still another preferred embodiment, the pH of the aqueoussolution A is 10.8 or less and 10.2 or greater in the method. In anotherembodiment, the chlorine dioxide (ClO₂) is provided as gas in themethod.

In one aspect, the present invention provides an article impregnatedwith the sterilizing agent of the present invention. An article that canbe used as the article of the present invention is any article that canbe impregnated with a chlorous acid aqueous solution to be used insterilization or the like, including medical devices. Examples thereofinclude, but are not limited to, a sheet, film, patch, brush, nonwovenfabric, paper, fabric, absorbent cotton, sponge and the like.

Thus, the present invention provides, in one aspect, a kit formanufacturing a chlorous acid aqueous solution, comprising (1) acontainer comprising chlorine dioxide and (2) a container comprising oneof an inorganic acid, inorganic acid salt, organic acid, and organicacid salt, two or more types thereof or a combination thereof.

In one preferred embodiment, the kit further comprises another (3)container comprising one of an inorganic acid, inorganic acid salt,organic acid, and organic acid salt, two or more types thereof or acombination thereof. (2) and (3) may be the same or different.

According to the present invention, chlorous acid (HClO₂) can be stablymaintained over a long period of time. Although not wishing to be boundby any theory, this is because it is understood that use of chlorinedioxide can create a transitional state and delay a decompositionreaction. Thus, a chlorous acid aqueous solution manufactured by thepresent manufacturing method is considered to have a longer lifespancompared to conventional chlorous acid aqueous solutions.

According to the present invention, chlorous acid having a high level ofsterilizing power can be stabilized for a long period of time. Thus, anaqueous solution comprising chlorous acid (so-called chlorous acidaqueous solution), which was generally difficult to distribute as aproduct, can now be distributed to the market and popularized in thesociety as a highly safe, useful and simple sterilizing agent.

Any reference document cited herein, such as a scientific article,patent or patent application, is incorporated herein by reference in thesame manner as the entire content of each document is specificallydescribed.

As described above, the present invention has been explained whilepresenting preferable embodiments to facilitate understanding.Hereinafter, the present invention is explained based on the Examples.However, the aforementioned explanation and the following Examples areprovided solely for exemplification, not for limiting the presentinvention. Thus, the scope of the present invention is not limited tothe Embodiments or Examples that are specifically described herein. Thescope of the present invention is limited solely by the scope of theclaims.

EXAMPLES

When necessary, animals used in the following Examples were handled incompliance with the Declaration of Helsinki. For reagents, the specificproducts described in the Examples were used. However, the reagents canbe substituted with an equivalent product from another manufacturer(Sigma, Wako Pure Chemical, Nacalai Tesque, or the like). There arecases herein where an abbreviation “CAAS” is used for a chlorous acidaqueous solution. However, they are synonymous.

Production Condition of Chlorous Acid Aqueous Solution)

The chlorous acid aqueous solution used in the following Examples isproduced as explained below.

(Example of Manufacturing Plant)

An example of a manufacturing plant used is shown in FIG. 1.

Each of the numbers in FIG. 1 is the member shown in the followingTable.

TABLE 1 Number Name 1 Chlorous acid aqueous solution manufacturing tank2 Gas washing device 3 Chlorine dioxide gas storage tank 4 Air pump 5Air flow spigot

The chlorine dioxide gas used (made by the Applicant) has aconcentration of 0.88%, and the acceptable range is preferably 0.9%±0.1%. Gas with a high concentration is dangerous due to itsexplosiveness. Thus, such gas is diluted with nitrogen gas or the likefor use. Further, the flow rate can be adjusted with 5, which is set at210 ppm/minute (210 ppm/min±40 ppm/min (660 mg·ClO₂/min to 530mg·ClO₂/min)) in the present Example.

(Blending Examples for Each Solution)

Blending examples of each solution that can be used in the presentmanufacturing example are described below.

TABLE 2 Table of blended ingredients a (CAAS A-1) Name of raw materialBlended amount (1) Tap water 731.88 g (2) Sodium hydroxide   2.5 g (3)Dipotassium hydrogenphosphate 139.36 g (4) Sodium carbonate    53 g (5)Sodium tetraborate (decahydrate)  7.62 g (6) 35% hydrogen peroxide    30g Total   1000 g

TABLE 3 Table of blended ingredients b (CAAS A-2) Name of raw materialBlended amount (1) Tap water 738.64 g (2) Potassium hydroxide  44.8 g(3) Dipotassium hydrogenphosphate 139.36 g (4) Succinic acid  47.2 g (5)35% hydrogen peroxide    30 g Total   1000 g

TABLE 4 Table of blended ingredients c (CAAS A-3) Name of raw materialBlended amount (1) Tap water  969 g (2) Sodium hydroxide   1 g (3) 35%hydrogen peroxide  30 g Total 1000 g

TABLE 5 Table of blended ingredient d (gas washing solution) Name of rawmaterial Blended amount (1) Tap water 910 g  (2) Sodium hydroxide 60 g(3) 35% hydrogen peroxide 30 g Total 1000 g 

Example 1: Manufacturing Example 1 of Chlorous Acid Aqueous Solution(CAAS A-1))

In Example 1, a chlorous acid aqueous solution was manufacturedaccording to the following procedure based on the conditions for CAASA-1 in (Production condition of chlorous acid aqueous solution).

(Method)

-   (1) Table of blended ingredient d was loaded into 2.-   (2) Table of blended ingredient a was loaded into 1. The pH of the    aqueous solution A was 10.8.-   (3) A tank containing 0.9%±0.1% chlorine dioxide gas was prepared    for 3.-   (4) 4 was put into operation.-   (5) 5 was released open to allow chlorine dioxide gas to flow into 1    at a flow rate of 210 ppm/minute (210 ppm/min±40 ppm/min (660    mg·ClO₂/min to 530 mg·ClO₂/min)).-   (6) 5 was closed after the gas has flowed in for 15 minutes.-   (7) 4 was stopped.-   (8) The mixture was left standing for 15 minutes.-   (9) 4 was again put into operation, and (4)-(8) were repeated 3 to 4    times (actual total time of chlorine dioxide gas flowing in was 45    to 60 minutes).-   (10) The liquid in 1 was named chlorous acid aqueous solution A-1

(Results)

The test results for the manufactured product are shown below.

TABLE 6 Chlorous acid aqueous solution A-1 Tested item SpecificationResult Potassium When potassium When potassium permanganate permanganatepermanganate solution solution (1→300) is (1→300) was added to 5 mladded to 5 ml of the of the present present product product (1→20), the(1→20), the mixture mixture turned reddish turns reddish purple. purple.When 1 ml of When 1 ml of sulfuric sulfuric acid (1→20) acid (1→20) isadded was added thereto, the thereto, the mixture mixture turned lightturns light yellow. yellow. UV spectrum An aqueous solution An aqueoussolution of of the present the present product had product has maximummaximum absorbance absorbance sections sections at at wavelengths 258 towavelengths 258 to 262 nm 262 nm and 346 to 361 nm. and 346 to 361 nm.Potassium When potassium iodide When potassium iodide iodide starchstarch paper is starch paper was paper immersed in the immersed in thepresent present product, the product, the potassium potassium iodideiodide starch paper starch paper changes changed to a blue color to ablue color and and then the color then the color fades. faded. Chlorousacid . . . 58285 ppm concentration

The UV spectrum is shown in FIG. 2. The UV spectrum, as shown, has adouble peak, confirming that a chlorous acid aqueous solution with asterilizing effect retained is correctly manufactured.

Example 2: Manufacturing Example 1 of Chlorous Acid Aqueous solutionformulation (CAAS A-1))

In Example 2, a chlorous acid aqueous solution formulation wasmanufactured according to the following procedure by using CAAS A-1 inExample 1.

Aqueous solution B was made based on the following.

TABLE 7 Name of raw material Blended amount (1) CAAS A-1 686.28 g (2)Dipotassium hydrogenphosphate  14.00 g (3) Ion exchange water 299.72 gTotal   1000 g

The pH at this time was 6.4.

TABLE 8 Chlorous acid aqueous solution formulation A-1 Tested itemSpecification Result Potassium When potassium When potassiumpermanganate permanganate permanganate solution solution (1→300) is(1→300) was added to 5 ml added to 5 ml of the of the present presentproduct product (1→20), the (1→20), the mixture mixture turned reddishturns reddish purple. purple. When 1 ml of When 1 ml of sulfuricsulfuric acid (1→20) acid (1→20) is added was added thereto, thethereto, the mixture mixture turned light turns light yellow. yellow. UVspectrum An aqueous solution An aqueous solution of of the present thepresent product had product has maximum maximum absorbance absorbancesections sections at at wavelengths 258 to wavelengths 258 to 262 nm 262nm and 346 to 361 nm. and 346 to 361 nm. Potassium When potassium iodideWhen potassium iodide iodide starch starch paper is starch paper waspaper immersed in the immersed in the present present product, theproduct, the potassium potassium iodide iodide starch paper starch paperchanges changed to a blue color to a blue color and and then the colorthen the color fades. faded. Chlorous acid . . . 40000 ppm concentration

The UV spectrum is shown in FIG. 3. The UV spectrum, as shown, has adouble peak, confirming that a chlorous acid aqueous solution with asterilizing effect retained is correctly manufactured.

Example 3: Manufacturing Example 2 of Chlorous Acid Aqueous Solution(CAAS A-2))

In Example 3, a chlorous acid aqueous solution was manufacturedaccording to the following procedure based on the conditions for CAARSA-2 in (Production condition of chlorous acid aqueous solution).

(Method)

-   (1) Table of blended ingredient d was loaded into 2.-   (2) Table of blended ingredient b was loaded into 1. The pH of the    aqueous solution A was 8.0.-   (3) A tank containing 0.9% ±0.1% chlorine dioxide gas was prepared    for 3.-   (4) 4 was put into operation.-   (5) 5 was released open to allow chlorine dioxide gas to flow into 1    at a flow rate of 210 ppm/minute (210 ppm/min±40 ppm/min (660    mg·ClO₂/min to 530 mg·ClO₂/min)).-   (6) 5 was closed after the gas had flowed in for 15 minutes.-   (7) 4 was stopped.-   (8) The mixture was left standing for 15 minutes.-   (9) 4 was again put into operation, and (4)-(8) were repeated 2 to 3    times (actual total time of chlorine dioxide gas flowing in was 30    to 45 minutes).-   (10) The liquid in 1 was considered a chlorous acid aqueous    solution.

The test results for the manufactured product are shown below.

TABLE 9 Table of blended ingredient b Chlorous acid aqueous solution A-2Tested item Specification Result Potassium When potassium When potassiumpermanganate permanganate permanganate solution solution (1→300) is(1→300) was added to 5 ml added to 5 ml of the of the present presentproduct product (1→20), the (1→20), the mixture mixture turned reddishturns reddish purple. purple. When 1 ml of When 1 ml of sulfuricsulfuric acid (1→20) acid (1→20) is added was added thereto, thethereto, the mixture mixture turned light turns light yellow. yellow. UVspectrum An aqueous solution An aqueous solution of of the present thepresent product had product has maximum maximum absorbance absorbancesections sections at at wavelengths 258 to wavelengths 258 to 262 nm 262nm and 346 to 361 nm. and 346 to 361 nm. Potassium When potassium iodideWhen potassium iodide iodide starch starch paper is starch paper waspaper immersed in the immersed in the present present product, theproduct, the potassium potassium iodide iodide starch paper starch paperchanges changed to a blue color to a blue color and and then the colorthen the color fades. faded. Chlorous acid . . . 43093 ppm concentration

The UV spectrum is shown in FIG. 4. The UV spectrum, as shown, has adouble peak, confirming that a chlorous acid aqueous solution with asterilizing effect retained is correctly manufactured.

Example 4: Manufacturing Example 2 of Chlorous Acid Aqueous SolutionFormulation (CAAS A-2))

In Example 4, a chlorous acid aqueous solution formulation wasmanufactured according to the following procedure by using CAAS A-2 inExample 3.

Aqueous solution B was made based on the following.

TABLE 10 Name of raw material Blended amount (1) Chlorous acid aqueoussolution A-2 928.22 g  (2) Potassium dihydrogenphosphate 17.32 g (3) Ionexchange water 54.46 g Total  1000 g

The pH at this time was 6.0.

TABLE 11 Chlorous acid aqueous solution formulation A-2 Tested itemSpecification Result Potassium When potassium When potassiumpermanganate permanganate permanganate solution solution (1→300) is(1→300) was added to 5 ml added to 5 ml of the of the present presentproduct product (1→20), the (1→20), the mixture mixture turned reddishturns reddish purple. purple. When 1 ml of When 1 ml of sulfuricsulfuric acid (1→20) acid (1→20) is added was added thereto, thethereto, the mixture mixture turned light turns light yellow. yellow. UVspectrum An aqueous solution An aqueous solution of of the present thepresent product had product has maximum maximum absorbance absorbancesections sections at at wavelengths 258 to wavelengths 258 to 262 nm 262nm and 346 to 361 nm. and 346 to 361 nm. Potassium When potassium iodideWhen potassium iodide iodide starch starch paper is starch paper waspaper immersed in the immersed in the present present product, theproduct, the potassium potassium iodide iodide starch paper starch paperchanges changed to a blue color to a blue color and and then the colorthen the color fades. faded. Chlorous acid . . . 40000 ppm concentration

The UV spectrum is shown in FIG. 5. The UV spectrum, as shown, has adouble peak, confirming that a chlorous acid aqueous solution with asterilizing effect retained is correctly manufactured.

Example 5: Manufacturing Example 3 of Chlorous Acid Aqueous Solution(CAAS A-3))

In Example 5, a chlorous acid aqueous solution was manufacturedaccording to the following procedure based on the conditions for CAARSA-3 in (Production condition of chlorous acid aqueous solution).

(Method)

-   (1) Table of blended ingredient d was loaded into 2.

(2) Table of blended ingredient c was loaded into 1. The pH of theaqueous solution A was 11.0.

-   (3) A tank containing 0.9%±0.1% chlorine dioxide gas was prepared    for 3.-   (4) 4 was put into operation.

(5) 5 was released open to allow chlorine dioxide gas to flow into 1 ata flow rate of 210 ppm/minute (210 ppm/min±40 ppm/min (660 mg·ClO₂/minto 530 mg·ClO₂/min)).

-   (6) 5 was closed after the gas had flowed in for 15 minutes.-   (7) 4 was stopped.-   (8) The mixture was left standing for 15 minutes.-   (9) 4 was again put into operation, and (4)-(8) were repeated 1 to 2    times (actual total time of chlorine dioxide gas flowing in was 15    to 30 minutes).-   (10) The liquid in 1 was considered a chlorous acid aqueous    solution.

The test results for the manufactured product are shown below.

TABLE 12 Chlorous acid aqueous solution A-3 Tested item SpecificationResult Potassium When potassium When potassium permanganate permanganatepermanganate solution solution (1→300) is (1→300) was added to 5 mladded to 5 ml of the of the present present product product (1→20), the(1→20), the mixture mixture turned reddish turns reddish purple. purple.When 1 ml of When 1 ml of sulfuric sulfuric acid (1→20) acid (1→20) isadded was added thereto, the thereto, the mixture mixture turned lightturns light yellow. yellow. UV spectrum An aqueous solution An aqueoussolution of of the present the present product had product has maximummaximum absorbance absorbance sections sections at at wavelengths 258 towavelengths 258 to 262 nm 262 nm and 346 to 361 nm. and 346 to 361 nm.Potassium When potassium iodide When potassium iodide iodide starchstarch paper is starch paper was paper immersed in the immersed in thepresent present product, the product, the potassium potassium iodideiodide starch paper starch paper changes changed to a blue color to ablue color and and then the color then the color fades. faded. Chlorousacid . . . 13000 ppm concentration

The UV spectrum is shown in FIG. 6. The UV spectrum, as shown, has adouble peak, confirming that a chlorous acid aqueous solution with asterilizing effect retained is correctly manufactured.

(Example 6: Manufacturing Example 3 of Chlorous Acid Aqueous SolutionFormulation (CAAS A-3))

In Example 6, a chlorous acid aqueous solution formulation wasmanufactured according to the following procedure by using CAARS A-3 inExample 5.

Aqueous solution B was made based on the following.

TABLE 13 Raw material Blend ratio Chlorous acid aqueous solution A-375.0% Potassium dihydrogenphosphate 1.4% Potassium hydroxide 0.6%Purified water 23.0% Total 100.0%

The pH at this time was 6.8.

The test results for the manufactured product are shown below.

TABLE 14 Chlorous acid aqueous solution formulation A-3 Tested itemSpecification Result Potassium When potassium When potassiumpermanganate permanganate permanganate solution solution (1→300) is(1→300) was added to 5 ml added to 5 ml of the of the present presentproduct product (1→20), the (1→20), the mixture mixture turned reddishturns reddish purple. purple. When 1 ml of When 1 ml of sulfuricsulfuric acid (1→20) acid (1→20) is added was added thereto, thethereto, the mixture mixture turned light turns light yellow. yellow. UVspectrum An aqueous solution An aqueous solution of of the present thepresent product had product has maximum maximum absorbance absorbancesections sections at at wavelengths 258 to wavelengths 258 to 262 nm 262nm and 346 to 361 nm. and 346 to 361 nm. Potassium When potassium iodideWhen potassium iodide iodide starch starch paper is starch paper waspaper immersed in the immersed in the present present product, theproduct, the potassium potassium iodide iodide starch paper starch paperchanges changed to a blue color to a blue color and and then the colorthen the color fades. faded. Chlorous acid . . . 10000 ppm concentration

The UV spectrum is shown in FIG. 7. The UV spectrum, as shown, has adouble peak, confirming that a chlorous acid aqueous solution with asterilizing effect retained is correctly manufactured.

Example 7: Sterilization Power Test/Stability Test

The following experiment was conducted to examine the effects of CAASformulations A-1 to A-2 manufactured in Examples 2 and 4.

For stability, a compound (called “ASC” herein) in which 1N hydrochloricacid was added to 6% sodium chlorite to adjust the pH to 2.3 to 2.9 wasused as a control. ASC, together with 2 types of chlorous acid aqueoussolution manufactured in Examples 2 and 4, was sealed and stored at 4°C. in a dark room to examine the stability.

In the test to examine the sterilization effect, a change over time insterilization effects immediately after manufacture, on day 5, and day10 was examined. The sterilization effect on E. coli was assessed by acarbolic acid coefficient.

To examine the chlorous acid concentration, iodometric titration wasperformed on ASC and the 2 types of chlorous acid aqueous solutionmanufactured in Examples 2 and 4 on day 1, day 5, and day 10 to find thechlorous acid concentration.

The results thereof are shown below.

TABLE 15-1 Sterilization effect examination table (ASC) Immediatelyafter manufacture Contact time % ppm 1 min. 5 min. 10 min. 15 min.Carbolic acid concentration 2.070% 20000 ppm   − − − − 1.500% 15000ppm   + − − − 1.000% 10000 ppm   + + − − 0.700% 7000 ppm  + + + + 0.500%5000 ppm  + + + + 0.300% 3000 ppm  + + + + 0.100% 1000 ppm  + + + +0.010% 100 ppm  + + + + Chlorous acid concentration 0.015% 150 ppm  − −− − 0.010% 100 ppm  − − − − 0.008% 80 ppm − − − − 0.007% 70 ppm − − − −0.006% 60 ppm − − − − 0.005% 50 ppm + − − − 0.004% 40 ppm + − − − 0.003%30 ppm + + + − 0.002% 20 ppm + + + + 0.001% 10 ppm + + + + 0.000%  0ppm + + + +

TABLE 15-2 Sterilization effect examination table (ASC) Day 5 Contacttime % ppm 1 min. 5 min. 10 min. 15 min. Carbolic acid concentration2.070% 20000 ppm  − − − − 1.500% 15000 ppm  + − − − 1.000% 10000ppm  + + − − 0.700% 7000 ppm + + + + 0.500% 5000 ppm + + + + 0.300% 3000ppm + + + + 0.100% 1000 ppm + + + + 0.010%  100 ppm + + + + Chlorousacid concentration 2.070% 20000 ppm  + + + + 1.500% 15000 ppm  + + + +1.000% 10000 ppm  + + + + 0.700% 7000 ppm + + + + 0.500% 5000ppm + + + + 0.300% 3000 ppm + + + + 0.100% 1000 ppm + + + + 0.010%  100ppm + + + + 0.005%  50 ppm + + + + 0.001%  10 ppm + + + + 0.000%   0ppm + + + +

TABLE 15-3 Sterilization effect examination table (ASC) Day 10 Contacttime % ppm 1 min. 5 min. 10 min. 15 min. Carbolic acid concentration2.070% 20000 ppm  − − − − 1.500% 15000 ppm  + − − − 1.000% 10000ppm  + + − − 0.700% 7000 ppm + + + + 0.500% 5000 ppm + + + + 0.300% 3000ppm + + + + 0.100% 1000 ppm + + + + 0.010%  100 ppm + + + + Chlorousacid concentration 2.070% 20000 ppm  + + + + 1.500% 15000 ppm  + + + +1.000% 10000 ppm  + + + + 0.700% 7000 ppm + + + + 0.500% 5000ppm + + + + 0.300% 3000 ppm + + + + 0.100% 1000 ppm + + + + 0.010%  100ppm + + + + 0.005%  50 ppm + + + + 0.001%  10 ppm + + + + 0.000%   0ppm + + + +

TABLE 16-1 Sterilization effect examination table (A-1) Immediatelyafter manufacture Contact time % ppm 1 min. 5 min. 10 min. 15 min.Carbolic acid concentration 2.070% 20000 ppm   − − − − 1.500% 15000ppm   + − − − 1.000% 10000 ppm   + + − − 0.700% 7000 ppm  + + + + 0.500%5000 ppm  + + + + 0.300% 3000 ppm  + + + + 0.100% 1000 ppm  + + + +0.010% 100 ppm  + + + + Chlorous acid concentration 0.015% 150 ppm  − −− − 0.010% 100 ppm  − − − − 0.008% 80 ppm − − − − 0.007% 70 ppm − − − −0.006% 60 ppm − − − − 0.005% 50 ppm − − − − 0.004% 40 ppm + + − − 0.003%30 ppm + + + + 0.002% 20 ppm + + + + 0.001% 10 ppm + + + + 0.000%  0ppm + + + +

TABLE 16-2 Sterilization effect examination table (A-1) Day 5 Contacttime % ppm 1 min. 5 min. 10 min. 15 min. Carbolic acid concentration2.070% 20000 ppm   − − − − 1.500% 15000 ppm   + − − − 1.000% 10000ppm   + + − − 0.700% 7000 ppm  + + + + 0.500% 5000 ppm  + + + + 0.300%3000 ppm  + + + + 0.100% 1000 ppm  + + + + 0.010% 100 ppm  + + + +Chlorous acid concentration 0.015% 150 ppm  − − − − 0.010% 100 ppm  − −− − 0.008% 80 ppm − − − − 0.007% 70 ppm − − − − 0.006% 60 ppm − − − −0.005% 50 ppm − − − − 0.004% 40 ppm + + − − 0.003% 30 ppm + + + − 0.002%20 ppm + + + + 0.001% 10 ppm + + + + 0.000%  0 ppm + + + +

TABLE 16-3 Sterilization effect examination table (A-1) Day 10 Contacttime % ppm 1 min. 5 min. 10 min. 15 min. Carbolic acid concentration2.070% 20000 ppm   − − − − 1.500% 15000 ppm   + − − − 1.000% 10000ppm   + + − − 0.700% 7000 ppm  + + + + 0.500% 5000 ppm  + + + + 0.300%3000 ppm  + + + + 0.100% 1000 ppm  + + + + 0.010% 100 ppm  + + + +Chlorous acid concentration 0.015% 150 ppm  − − − − 0.010% 100 ppm  − −− − 0.008% 80 ppm − − − − 0.007% 70 ppm − − − − 0.006% 60 ppm − − − −0.005% 50 ppm − − − − 0.004% 40 ppm + + − − 0.003% 30 ppm + + + + 0.002%20 ppm + + + + 0.001% 10 ppm + + + + 0.000%  0 ppm + + + +

TABLE 17-1 Sterilization effect examination table (A-2) Immediatelyafter manufacture Contact time % ppm 1 min. 5 min. 10 min. 15 min.Carbolic acid concentration 2.070% 20000 ppm   − − − − 1.500% 15000ppm   + − − − 1.000% 10000 ppm   + + − − 0.700% 7000 ppm  + + + + 0.500%5000 ppm  + + + + 0.300% 3000 ppm  + + + + 0.100% 1000 ppm  + + + +0.010% 100 ppm  + + + + Chlorous acid concentration 0.015% 150 ppm  − −− − 0.010% 100 ppm  − − − − 0.008% 80 ppm − − − − 0.007% 70 ppm − − − −0.006% 60 ppm − − − − 0.005% 50 ppm − − − − 0.004% 40 ppm − − − − 0.003%30 ppm + + − − 0.002% 20 ppm + + + + 0.001% 10 ppm + + + + 0.000%  0ppm + + + +

TABLE 17-2 Sterilization effect examination table (A-2) Day 5 Contacttime % ppm 1 min. 5 min. 10 min. 15 min. Carbolic acid concentration2.070% 20000 ppm   − − − − 1.500% 15000 ppm   + − − − 1.000% 10000ppm   + + − − 0.700% 7000 ppm  + + + + 0.500% 5000 ppm  + + + + 0.300%3000 ppm  + + + + 0.100% 1000 ppm  + + + + 0.010% 100 ppm  + + + +Chlorous acid concentration 0.015% 150 ppm  − − − − 0.010% 100 ppm  − −− − 0.008% 80 ppm − − − − 0.007% 70 ppm − − − − 0.006% 60 ppm − − − −0.005% 50 ppm − − − − 0.004% 40 ppm − − − − 0.003% 30 ppm + + − − 0.002%20 ppm + + + + 0.001% 10 ppm + + + + 0.000%  0 ppm + + + +

TABLE 17-3 Sterilization effect examination table (A-2) Day 10 Contacttime % ppm 1 min. 5 min. 10 min. 15 min. Carbolic acid concentration2.070% 20000 ppm   − − − − 1.500% 15000 ppm   + − − − 1.000% 10000ppm   + + − − 0.700% 7000 ppm  + + + + 0.500% 5000 ppm  + + + + 0.300%3000 ppm  + + + + 0.100% 1000 ppm  + + + + 0.010% 100 ppm  + + + +Chlorous acid concentration 0.015% 150 ppm  − − − − 0.010% 100 ppm  − −− − 0.008% 80 ppm − − − − 0.007% 70 ppm − − − − 0.006% 60 ppm − − − −0.005% 50 ppm − − − − 0.004% 40 ppm − − − − 0.003% 30 ppm + + − − 0.002%20 ppm + + + + 0.001% 10 ppm + + + + 0.000%  0 ppm + + + +

The advantage in using gaseous chlorine dioxide (gas) includes thefollowing: a transitional state is created and a decomposition reactionis delayed such that chlorous acid (HClO₂) can be stably maintained overa long period of time.

FIG. 8 shows a graph of results summarizing the above.

As shown in Tables 15-1 to 15-3 and FIG. 8, the chlorous acid aqueoussolution concentration in the control, ASC, has nearly disappeared onday 5, and the sterilization effect on E. coli has also disappeared.Meanwhile, as shown in Tables 16-1 to 16-3, 17-1 to 17-3 and FIG. 8, thechlorous acid aqueous solution concentration of chlorous acid aqueoussolution formulation A-1 and chlorous acid aqueous solution formulationA-2 dramatically decreased immediately after manufacture, but stabilizedthereafter despite with a gradual decrease. The sterilization effect onE. coli was also maintained. Since there is hardly any difference in thesterilization effect when data for immediately after manufacture and day10 are compared, it is understood as a manufacturing method of achlorous acid aqueous solution which can stably exhibit a sterilizingeffect for at least 10 days. Although not wishing to be bound by anytheory, this has demonstrated that a chlorous acid aqueous solutionmanufactured by the manufacturing method of the present inventioncreates a transitional state and delays a decomposition reaction suchthat chlorous acid (HClO₂) is stably maintained in an aqueous solutionover a long period of time.

As described above, the present invention is exemplified by the use ofits preferred Embodiments and Examples. However, the present inventionis not limited thereto. Various embodiments can be practiced within thescope of the structures recited in the claims. It is understood that thescope of the present invention should be interpreted solely based on theclaims. Furthermore, it is understood that any patent, any patentapplication, and references cited herein should be incorporated hereinby reference in the same manner as the content are specificallydescribed herein.

INDUSTRIAL APPLICABILITY

An aqueous solution comprising a chlorous acid aqueous solution obtainedby the present invention can be utilized in applications such assterilizing agents as well as deodorants, bleaching agents, blood stainremoving agents, and the like.

1. A method of manufacturing a chlorous acid aqueous solution,comprising the step of: trapping chlorine dioxide (ClO₂) with aqueoussolution A comprising one of an inorganic acid, inorganic acid salt,organic acid, and organic acid salt, two or more types thereof or acombination thereof.
 2. The method of claim 1, further comprising thestep of adding the chlorine dioxide in the presence of hydrogenperoxide.
 3. The method of claim 1, wherein a pH of the aqueous solutionA is 11.0 or less and 6.0 or greater.
 4. The method of claim 1, whereina pH of the aqueous solution A is 10.8 or less and 10.2 or greater. 5.The method of claim 1, wherein the chlorine dioxide (ClO₂) is providedas gas.
 6. The method of claim 1, comprising, after the step of adding,a step of further adding aqueous solution B comprising one of aninorganic acid, inorganic acid salt, organic acid, and organic acidsalt, two or more types thereof or a combination thereof.
 7. The methodof claim 1, wherein the inorganic acid is carbonic acid, phosphoricacid, boric acid, or sulfuric acid; and the inorganic acid salt iscarbonate, hydroxide, phosphate, or borate.
 8. The method of claim 7,wherein the carbonate is sodium carbonate, potassium carbonate, sodiumbicarbonate, or potassium bicarbonate, and the hydroxide is sodiumhydroxide, potassium hydroxide, calcium hydroxide, or barium hydroxide.9. The method of claim 7, wherein the phosphate is disodium hydrogenphosphate, sodium dihydrogen phosphate, trisodium phosphate,tripotassium phosphate, dipotassium hydrogen phosphate, or potassiumdihydrogen phosphate.
 10. The method of claim 7, wherein the borate issodium borate or potassium borate.
 11. The method of claim 1, whereinthe organic acid salt is succinic acid, citric acid, malic acid, aceticacid, or lactic acid.
 12. The method of claim 1, wherein the organicacid salt is sodium succinate, potassium succinate, sodium citrate,potassium citrate, sodium malate, potassium malate, sodium acetate,potassium acetate, sodium lactate, potassium lactate, or calciumlactate.
 13. The method of claim 1, wherein TAL of the aqueous solutionA is 20 to 2000, wherein the TAL is found by an amount of 0.1N—HCltitration from an initial pH at or below pH of 11.0 to a pH of
 14. Themethod of claim 6, wherein a pH of a liquid after adding the aqueoussolution B is 3.2 or greater and less than 7.0, or a pH of a liquidafter adding the aqueous solution B is 4.0 or greater and less than 7.0,or a pH of a liquid after adding the aqueous solution B is about 5.0 orgreater and less than 7.0.
 15. The method of claim 1, wherein thechlorine dioxide is present at a concentration of 0.8 to 1.0%.
 16. Achlorous acid aqueous solution manufactured by a method comprising thestep of trapping chlorine dioxide (ClO₂) with aqueous solution Acomprising one of an inorganic acid, inorganic acid salt, organic acid,and organic acid salt, two or more types thereof or a combinationthereof.
 17. The chlorous acid aqueous solution of claim 16, wherein themethod further comprises a step of adding the chlorine dioxide in thepresence of hydrogen peroxide.
 18. The chlorous acid aqueous solution ofclaim 16, wherein a pH of the aqueous solution A is 11.0 or less and 6.0or greater.
 19. The chlorous acid aqueous solution of claim 16, whereina pH of the aqueous solution A is 10.8 or less and 10.2 or greater. 20.The chlorous acid aqueous solution of claim 16, wherein the chlorinedioxide (ClO₂) is provided as gas. <PCT claim 24>